This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 2002-262835 filed in Japan on Sep. 9, 2002, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a solid-state image pick-up device including a plurality of photoelectric converting devices provided like a tetragonal grid in a row direction and a column direction orthogonal thereto over the surface of a semiconductor substrate.
2. Description of the Related Art
A solid-state image pick-up device to be utilized for a digital camera detects a charge corresponding to an image signal by means of a photoelectric converting device. For this reason, in general, it is hard to widen a dynamic range. In order to obtain an image in a wide dynamic range, it is necessary to increase the amount of charges to be detected by the photoelectric converting device. For this purpose, it is necessary to increase the light receiving area of the photoelectric converting device. When the amount of the charges to be detected is increased, however, it is necessary to increase a transfer capacity, that is, a dimension of a charge transfer section. Consequently, there is a problem in that the number of pick-up images cannot be increased.
FIG. 11 shows a schematic structure according to an example of a conventional solid-state image pick-up device. The solid-state image pick-up device in FIG. 11 serves to convert a light intensity into a charge signal by a plurality of photoelectric converting devices 10 provided like a tetragonal grid, and a detected signal charge is transferred to an output section 40 through a plurality of vertical transfer sections 20 (In FIG. 11, one vertical transfer section is surrounded in a broken line) and a horizontal transfer section 30 and a voltage signal 41 corresponding to the signal charge is output from the output section 40.
The vertical transfer section 20 serves to transfer charges from the photoelectric converting devices 10 in a column direction Y and includes a plurality of vertical transfer channels (not shown) formed on a semiconductor substrate, a plurality of vertical transfer electrodes 101 to 104 formed on the upper layers of the vertical transfer channels, and a charge reading region 21 for reading the charges of the photoelectric converting devices 10 onto the vertical transfer channels (which are typically shown in an arrow of FIG. 11).
The vertical transfer channels take an almost straight shape extended in the column direction Y toward the side of the photoelectric converting devices 10, and a region for storing and transferring the charge is partitioned by the vertical transfer electrodes 101 to 104 formed on upper layers thereof. Two vertical transfer electrodes 101 to 104 are provided corresponding to the respective photoelectric converting devices 10 (only any of them corresponding to the photoelectric converting devices for two rows has the designation in FIG. 11) and the vertical transfer electrodes having the same positional relationship with the photoelectric converting devices for the same row are electrically connected through electrode wirings 121 and 122. The vertical transfer electrodes 101 to 104 are formed of polycrystalline silicon.
Vertical transfer pulses having four phases are applied to the vertical transfer electrodes 101 to 104 through terminals 11 to 14 and the charges of the vertical transfer channels are transferred in the column direction Y. The vertical transfer pulse is also applied to transfer electrodes 105, 106 and 107 between the vertical transfer section 20 and the horizontal transfer section 30, and the charges for one row which are detected by the photoelectric converting devices 10 for an odd row or the photoelectric converting devices 10 for an even row are sent to the horizontal transfer section 30. The reading operation of the photoelectric converting devices 10 for the odd row is carried out by superposing a reading pulse on a first-phase pulse to be applied immediately before the start of a vertical charge transfer (a vertical transfer pulse to be applied to the terminal 11), and the reading operation of the photoelectric converting devices 10 for the even row is carried out by superposing a reading pulse on a third-phase pulse to be applied immediately after the start of the vertical charge transfer (a vertical transfer pulse to be applied to the terminal 13).
The horizontal transfer section 30 serves to transfer a charge from the vertical transfer section 20 in a row direction X and includes a horizontal transfer channel and a horizontal transfer electrode (which are not shown). Horizontal transfer pulses having two phases are applied to the horizontal transfer electrode through terminals 131 and 132 and the signal charges of the photoelectric converting devices 10 for one row which are sent from the vertical transfer section 20 are transferred to the output section 40.
Next, description will be given to the driving operation of the solid-state image pick-up device shown in FIG. 11. Referring to charges stored in the photoelectric converting device 10 corresponding to the intensity of a light incident from a field, first of all, the charges stored in the photoelectric converting devices 10 for the odd row are read onto the vertical transfer channel in response to the reading pulse to be superposed on the first-phase vertical transfer pulse. Then, the charges are transferred in the vertical transfer channel in response to the vertical transfer pulse and are held in the predetermined region of the horizontal transfer channel. Subsequently, when the horizontal transfer pulse is applied, the held charges for one row are sequentially sent to the output section 40 and the voltage signal 41 corresponding to the amount of the charges is output. After such a transfer processing is carried out for all of the photoelectric converting devices 10 for the odd rows, a reading pulse is superposed on the third-phase vertical transfer pulse to read the charges stored in the photoelectric converting devices 10 for the even rows onto the vertical transfer channel, thereby carrying out the same transfer.
In the conventional solid-state image pick-up device shown in FIG. 11, a region between the photoelectric converting devices in a vertical direction is utilized as the wiring path of the vertical transfer electrode and an image pick-up device is a useless region. More specifically, the ratio of the area of the photoelectric converting device to play a part in light concentration and charge storage and the area of the vertical transfer channel to play a part in the transfer of a signal charge to an area per pixel has an upper limit. For this reason, it is hard to raise the sensitivity of a pick-up image and a saturation voltage.
When the amount of the signal charge to be detected by the photoelectric converting device is increased, however, it is necessary to increase the channel width of the charge transfer channel. Conventionally, the charge transfer channel is provided on only the side of the photoelectric converting device. Consequently, the light receiving region of the photoelectric converting device becomes rectangle-shaped. In general, a microlens is provided for the light concentration above the photoelectric converting device 10. If the shape of the light receiving region is rectangular, it is hard to concentrate an incident light in the photoelectric converting device by means of the microlens. Consequently, there is a problem in that shading is increased, resulting in a remarkable reduction in the sensitivity with a small F value.
Patent Document JP-A-5-291552 has described a solid-state image pick-up device in which a charge transfer section has a winding shape between photoelectric converting devices to enlarge a dynamic range. In this solid-state image pick-up device, the photoelectric converting device is to be provided in winding shape, and furthermore, the shape of the vertical transfer section is varied between the adjacent photoelectric converting device strings. Accordingly, there is a problem in that it is hard to cause characteristics to be coincident with each other and an unevenness is apt to be generated in an image pick-up signal which is obtained.
The invention has been made in consideration of the circumstances and has an object to provide a solid-state image pick-up device having such a simple structure that the ratio of the areas of a photoelectric converting device and a vertical transfer channel to the area of a whole image pick-up section can be increased to obtain a great saturation output with a high sensitivity.
The invention provides a solid-state image pick-up device having a plurality of photoelectric converting devices arranged like a checker board in a row direction and a column direction orthogonal thereto over a surface of a provided corresponding to a plurality of photoelectric converting device strings having the photoelectric converting devices arranged in the column direction respectively and serving to transfer a charge of the photoelectric converting device in the column direction, a horizontal transfer section for transferring the charge from the vertical transfer section in the row direction, and an output section for outputting a signal corresponding to the charge to be transferred by the horizontal transfer section, wherein the vertical transfer section includes a vertical transfer channel and a plurality of vertical transfer electrodes provided on an upper layer of the vertical transfer channel, the vertical transfer channel is provided in winding shape between the photoelectric converting devices constituting the corresponding photoelectric converting device string, the vertical transfer electrode includes a first vertical transfer electrode having a first conductive layer formed on the upper layer of the vertical transfer channel between the photoelectric converting devices and a second vertical transfer electrode having a second conductive layer formed on the upper layer of the vertical transfer channel on a side of the photoelectric converting device, and the first vertical transfer electrode and the second vertical transfer electrode corresponding to the photoelectric converting devices for the same row are driven in response to driving signals having the same phase, respectively.
According to such a solid-state image pick-up device, the almost whole periphery of the photoelectric converting device can be utilized as the vertical transfer channel. Consequently, it is possible to increase the areas of the photoelectric converting device and the vertical transfer channel to the area of the whole image pick-up section, thereby obtaining a great saturation output with a high sensitivity.
In the solid-state image pick-up device according to the invention, the vertical transfer channel is formed with the same arrangement and shape for the photoelectric converting device strings. With such a structure, the charge transfer characteristic of the vertical transfer section can be made uniform so that even image data can be obtained easily.
In the solid-state image pick-up device according to the invention, a charge reading region for reading the charge of the photoelectric converting device onto the vertical transfer channel is formed in contact with the vertical transfer channel on the side of the photoelectric converting device.
In the solid-state image pick-up device according to the invention, moreover, a charge reading region for reading the charge of the photoelectric converting device onto the vertical transfer channel is formed in contact with the vertical transfer channel between the photoelectric converting devices.
Furthermore, the charge reading region for reading the charge of the photoelectric converting device onto the vertical transfer channel is formed in contact with the vertical transfer channel between the photoelectric converting devices, and a position of the charge reading region with respect to the photoelectric converting device is identical for each of the photoelectric converting device strings and the positions of the photoelectric converting device strings which are adjacent to each other are different from each other. According to the solid-state image pick-up device, the charges of the photoelectric converting devices in the checked position can be read at the same time so that uniform thinning reading can be carried out.
In addition, two kinds of collecting microlenses having different collection ratios are provided corresponding to each of the photoelectric converting devices, and the two kinds of microlenses are provided like a checker, respectively. With such a structure, it is possible to separately output a detection signal for a high-sensitivity pixel and a detection signal to be a low-sensitivity pixel signal which are arranged in checked positions, respectively.
The invention provides a solid-state image pick-up device having a plurality of photoelectric converting devices arranged like a tetragonal grid in a row direction and a column direction orthogonal thereto over a surface of a semiconductor substrate, comprising a plurality of vertical transfer sections provided corresponding to a plurality of photoelectric converting device strings having the photoelectric converting devices arranged in the column direction respectively and serving to transfer a charge of the photoelectric converting device in the column direction, a horizontal transfer section for transferring the charge from the vertical transfer section in the row direction, and an output section for outputting a signal corresponding to the charge to be transferred by the horizontal transfer section, wherein the vertical transfer section includes a vertical transfer channel and a plurality of vertical transfer electrodes provided on an upper layer of the vertical transfer channel, the vertical transfer channel includes a first portion provided on a side of each of the photoelectric converting devices constituting the corresponding photoelectric converting device string and a second portion provided between the photoelectric converting devices and wholly has a shape of a comb, the vertical transfer electrode includes a first vertical transfer electrode having a first conductive layer formed on the upper layer of the vertical transfer channel between the photoelectric converting devices and a second vertical transfer electrode having a second conductive layer formed on the upper layer of the vertical transfer channel on a side of the photoelectric converting device, and the first vertical transfer electrode and the second vertical transfer electrode corresponding to the photoelectric converting devices for the same row are driven in response to driving signals having the same phase, respectively. With such a structure, the close portions of the adjacent vertical transfer channels have no bent section. Consequently, restrictions on a design are less imposed and the charge transfer can be carried out smoothly.
In the solid-state image pick-up device according to the invention, a downstream end of the transfer channel provided below the first vertical transfer electrode is formed to be almost coincident with an end of the first portion having a small channel width which is positioned on a downstream thereof. Consequently, the storage region of the portion having a small channel width is enlarged into a portion having a great channel width. Thus, the charge transfer from the second portion to the first portion in the vertical transfer channel can be carried out smoothly.
In the solid-state image pick-up device according to the invention, a light receiving region of the photoelectric converting device has such a shape that an aspect ratio is approximately 1. With such a shape, a light concentration can be carried out efficiently by means of a microlens. By reducing shading, it is possible to avoid a reduction in a sensitivity with a small F value. The microlens can easily be designed. By changing the size of the microlens, therefore, it is possible to easily obtain an image pick-up device in which a high sensitivity pixel and a low sensitivity pixel are arranged.